Re: [PATCH 05/15] RDS: increase size of hash-table to 8K

From: santosh shilimkar
Date: Mon Sep 21 2015 - 19:55:41 EST


On 9/21/2015 4:05 PM, David Miller wrote:
From: Santosh Shilimkar <santosh.shilimkar@xxxxxxxxxx>
Date: Sat, 19 Sep 2015 19:04:42 -0400

Even with per bucket locking scheme, in a massive parallel
system with active rds sockets which could be in excess of multiple
of 10K, rds_bin_lookup() workload is siginificant because of smaller
hashtable size.

With some tests, it was found that we get modest but still nice
reduction in rds_bind_lookup with bigger bucket.

Hashtable Baseline(1k) Delta
2048: 8.28% -2.45%
4096: 8.28% -4.60%
8192: 8.28% -6.46%
16384: 8.28% -6.75%

Based on the data, we set 8K as the bind hash-table size.

Signed-off-by: Santosh Shilimkar <ssantosh@xxxxxxxxxx>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@xxxxxxxxxx>

Like others I would strongly prefer that you use a dynamically sized
hash table.

Eating 8k just because a module just happened to get loaded is really
not appropriate.

And there are many other places that use such a scheme, one example is
the AF_NETLINK socket hash table.

OK. Thanks for AF_NETLINK pointer. I will look it up.

Regards,
Santosh
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